Fluorinated and Nanoporous Graphene Materials As Sorbents for Gas Separations
J Schrier, ACS APPLIED MATERIALS & INTERFACES, 3, 4451-4458 (2011).
The physisorption of gases on surfaces depends on the electrostatic and dispersion interactions with adsorbates. The former can be tuned by introducing charge variations in the material, and the latter can be tuned by chemical substitution. Using atomistic Monte Carlo calculations, the Henry's law constants, and isosteric heats of adsorption of CH(4), CO(2), N(2), O(2), H(2)S, SO(2), and H(2)O on graphene, two-dimensional polyphenylene (2D-PP), fluorographene, and fluoro(2D-PP) surfaces are used to demonstrate the tunability of these two types of interaction. With the exception of H(2)O, fluorination and nanoporosity-induced charge variations reduce the binding of the adsorbates. Gas separations relevant for CO(2) sequestration, biogas upgrading, SO(2) pollution control, and air dehumidification are considered, and in most cases, the nanoporosity and fluorination reduce the selectivity of adsorption. The exceptions are separations involving adsorption of H(2)O and the SO(2)/N(2) separation, where the large dipole moments of the adsorbed species leads to enhanced binding relative to the nonpolar species.
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